Pulse keying circuit



May 25, 1948. MAYLE 4 2,442,304

PULSE KEYING CIRCUIT Filed Jan. 17, 1944 POWER AMPLIFiER INVENTOR rLOUIS F. MAYLE Patented May 25, 1948 PAT ENT ornce PULSE KEYING CIRCUITLouis -F. Mayle, Fort Wayne, Ind., assignor, by

mcsne assignments, to Farnsworth Research Corporation, a; corporationofIndiana Application January 17, 1944; seriarNo; 518,534

4' Claims. 1;

invention: relates generally to synchronizing circuits and moreparticularly to-a: pulse keying-circuit for keying; a power ampli-fiercircu'it to=produce carrier modulations correspondingato synchronizingsignals.

Prior art pulse generating circuits generally include aplurality ofamplifying tubes for increasing: the e'fiective' amplitude of asynchro-- nizi-ng-lpul'se. Theefficiency-of such" a system isnecessarilyilow by reason'of' the-number of tubes involved. Therefore;it would bedesira'ble to obtain. a simplified circuit comprising aminimum number-"oi-tubes for generating pulses-of the requiredamplitude;

Theiprincipal object of this invention is" to pro vide:anove1:synchronizing pulse keying circuit fo'rikey-in'g a-poweramplifiercircuit.

A further objector theinvention-is to provide asimplified: pulse keyingcircuit: wherein the number of" circuitcomponents is =materially reduced and wherein there is provided a "comparatively high amplitudesynchronizing pulse.

In general; the invention comprises an ampliher for amplifying pulsesgenerated by-apulse generator; axgas'discharge-keying device includin'ga storagefcondenser connected to its cathode together: witha diode:connected in the output circuitlof the gas. discharge tube in serieswith The storage condenser isflin' turns connected to the anode'circuitof a power: amplifier such,- for example, as a carrier:

the storage condenser.

frequency: amplifier" stage in'sa transmitter circuitz- The" storagecondenser normally charged to approximately 750 volts, and when the gasdischarge tubeis fired the voltage on the" storage condense'r isincreased byapproximately 750 voltswhereby there is produced; in"addition to the anode voltage of I the power: amplifier; a -voltage:the-charge on the" storage con denser; thereis producedra high amplituderepresented 1 by variation; inthe carrier signal to betransmitted,representative of the synchronizing pulse.

For a-betten understanding of the invention,-

together with otherandifurther objects thereof; reference is-made tothefollowing description;

taken: in connection with: tha accompanying.-

drawings, andiits 'scope'will' be pointed" out in the appended'claimsi-In the accompanying drawings the single-fig? pledb'y rneans of'condenseranamplifier-triode 4, There is provided a grid leal resistor 5,connected betweenground and the grid of tube 4; together-with'a-c'athode resistor 6 and shunt condenser 1 connected between thecathode and ground; Resistor's li'and IitOget'her with condenser T areprovided to energize triode 4 in a conventional manner.

The anode of-tube i is 'energ-ized'through a loadresistor'flfrom-voltage source Band is coupled to the control grid of agas'discharge tube I2 through a coupling condenser M. The anode circuit isalso coupled tothe anode of tube [2 by a condenser l5;- Thereis provideda grid rosisto'r I6 connected to groundthrough resistor l8 In serieswith the cathode'oitubel2 and resistor Hi, there is provided a resistor20 whereby to provide a cathode follower circuit. Source 9 is-conn'ectedthrough resistor 2| directly to thecatho'deof tube l2 for normallybiasing the tube below the threshold of firing. The'anode circuit oftube: Itineluclesa source of potential 24 tog-ether'with aninductance'coil 25; Between the inductance coil 25 and the cathode oftube l2 there is connected a storage condenser 28 and a diod'e rectifier30'. The output of the entire circuit is taken' off the'commonconnection between thecathode'of tube 30' and theconde'nser 2-8 andapplied to the anode circuit of power amplifier 3-2: Amplifier 32' isillustrated to represent any convenient-stage of a carrier frequencyamplifier'in a television transmitter whereby'condenser 28 may beconnected to any desirable stage of such an amplifier.

Assuming} that the operation of the circuit commences at a" time betweensynchronizin pulses, the gas discharge tube I2 is nonconducting byreason of-the fact that current flows from;

source 9 through resistor 2|, resistor 20 and ,re-

-sist0r l8 to ground whereby the voltage dIQp across resistor- 'm holdsgas discharge tube 12- biased below thethreshold of firing. Meanwhile,

condenser 28 is charged to approximately 750" volts with=respecttoground through rectifier'30';

When a negative'pulse from source l'isimpressed on the-"grid; of tube 4through coupling condenser 2, a positive pulse results in the anodecircuit of tube 4 which is impressed on the control grid of gasdischarge tube 12 through condenser Hi and also on the anode of tube 12through condenser l5, The leading edge of this pulse raises thepotential of the grid to fire the gas tube l2, and in addition theleading edge of the pulse impressed on the series combination ofcondenser i and inductance coil 2-5 will produce positive transient onthe anode of tube l2 to facilitate firing of the tube.

The trailing edge of the positive pulse appearing in the anode circuitof tube 4' will have no efiect on the control grid of tube 12, but thetrailing edge of the pulse effects the generation of a transientnegative pulse on the anode of tube 82, thereby to reduce momentarilythe potential of the anode and interrupt the flow of current through thetube to extinguish it.

During nonconductive periods of tube I2, current flows from source 24through rectifier 30 to the anode circuit of power amplifier 32 andbecause the internal resistance of tube 30 is extremely small during itsconductive periods, the plate of condenser 28 which is connected to thecathode of rectifier 30 is at the voltage of source 24. When gas tube I2is fired, its resistance also becomes substantially nil so that theplate of condenser 28 which is connected to the cathode of tube 12 israised in voltage from the voltage corresponding to the normal dropthrough resistors 20 and I 3 to the voltage of source 24. In eiTect,this is a switching or reversing operation wherein tubes i2 and 30constitute electronic switching devices. The voltage on the other plateof condenser 28 is raised proportionately until it is substantiallydouble the normal value. Because of the increased potential on condenser28 and on the cathode of tube 30, this tube becomes inoperative duringthe periods that tube I2 is conductive and during these same periods thepotential on the anode circuits of power ampliher 32 is substantiallydoubled. Thus the carrier signal in the amplifier circuit is keyed toinclude high amplitude variations representative of syn chronizingpulses.

When tube [2 is extinguished by the trailing edge of the synchronizingpulse impressed on the grid and plate thereof, the plate of condenser 28which is connected to the cathode of tube [2 assumes the normalpotential impressed thereon by source s whereby rectifier 30 againbecomes conductive to supply normal voltage to amplifier 32.

It is not intended that this invention shall be limited to the use ofany particular circuit elements or circuit values, but purely by way ofexample there follows a table of circuit values which it is believedwould cause the herein described circuit to operate in accordance withthe foregoing.

Resistor 20 1,000 ohms 4 Resistor 2| 50,000 ohms Source 24 750 voltsInductance coil 25 microhenries Condenser 28 1 microfarad Tube 30 Type5Y3GT While there has been described what is at present considered thepreferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

I claim:

1. In combination, a power ampilfier including an anode circuit, acharge storage device connected to said anode circuit, a source ofpotential and a rectifier connected to said anode circuit and saidcharge storage device for applying operating potential to said anodecircuit and for charging said charge storage device to a predeterminedpotential, a gas discharge tube including a cathode, a control grid andan anode, said anode being connected to said source of po tential andsaid cathode being connected to said charge storage device, a source ofpotential connected for normally biasing said discharge tubeinoperative, and a source of pulses connected to the control grid andanode of said discharge tube for periodically firing and extinguishingsaid discharge tube thereby to intermittently connect said first sourceof potential to said charge storage device for impressing increasedpotential on said power amplifier anode circuit.

2. A pulse keying circuit comprising a source of pulses, a gas dischargetube including a grid, cathode and anode, means connected between saidgrid and said source for impressing pulses on said grid, means connectedbetween said source and the anode of said gas discharge tube forimpressing pulses on the anode of said tube and means connected to saidanode and responsive to said pulses for generating transient voltagescorresponding to the leading and trailing edges of said pulses forfiring and extinguishing said tube.

3. A pulse keying circuit comprising a source of pulses, a gas dischargetube including a grid, cathode and anode, coupling means connectedbetween said grid and said source for impressing pulses on said grid andfiring said tube, coupling means connected between said source and theanode of said gas discharge tube for impressing pulses on the anode ofsaid tube and impedance means connected to said anode and responsive tosaid pulses for generating transient voltages corresponding to theleading and trailing edges of said pulses for firing and extinguishingsaid tube.

4. A synchronizing pulse keying circuit comprising a source ofsynchronizing pulses, a gas discharge tube including a grid, cathode andanode, coupling means connected between said grid and said source forimpressing pulses on said grid and firing said tube, coupling meansconnected between said source and the anode of said gas discharge tubefor impressing pulses on the anode of said tube, impedance meansconnected to said anode and responsive to said pulses for generatingtransient voltages corresponding to the leading and trailing edges ofsaid pulses for firing and extinguishing said tube, a signal outputcircuit, rectifier means connected between said anode impedance and saidoutput circuit and charge storage means connected between the cathode ofsaid gas discharge tube and said output circuit whereby one plate ofsaid charge storage means is normally at a certain potential when saiddischarge tube is non-conductive and at a higher potential when saiddischarge tube is conductiv LOUIS F. MAYLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 6 UNITED STATES PATENTS Name Date Blomberg May 2, 1933 Cockcroftet a1. Feb. 26, 1935 Schade Mar. 2, 1937 FitzGerald Apr. 27, 1937Burnside Nov. 26, 1942 Jones Apr. 29, 1941 Baldwin Oct. 14, 1941 RobinsMay 26, 1942 Livingston Oct. 5, 1943

